Exhaust-gas turbocharger having a ball-cock waste-gate valve with a stress-relieved crank arm

Abstract

An exhaust-gas turbocharger has a turbine housing and a waste-gate valve of a ball-cock configuration which is arranged therein. The actuating crank of the waste-gate valve has a crank arm, to which the closing element is fastened, and a crank spindle which is connected integrally to the crank arm and is mounted in the turbine-housing wall. A stop shoulder for sealing the crank-spindle bearing and a flexural-stress relief pocket are provided in the transition region between the crank spindle and the crank arm, as a result of which the sealing action of the crank-spindle bearing and a more uniform distribution of flexural stresses in the transition region between the crank arm and the crank spindle are brought about and therefore an increased service life of the actuating crank is ensured with a simultaneously economical configuration.

The invention claimed is: 
     
       1. An exhaust-gas turbocharger, comprising:
 a turbine housing having a turbine housing wall; 
 a wastegate valve disposed in said turbine housing, said wastegate valve being a ballcock-type valve having a spherical-segment-shaped closing element; and 
 an actuating crank having a crank arm to which said closing element is fastened, and a crank spindle integrally connected to said crank arm, said actuating crank mounted in said turbine housing wall so as to be rotatable about a crank spindle axis of rotation, said actuating crank further having an abutment shoulder disposed in a transition region between said crank spindle and said crank arm, said crank arm having a flexural-stress relief pocket formed therein, wherein adjoining said abutment shoulder on an inner side of said crank arm directed toward said turbine housing wall there is disposed said flexural-stress relief pocket for effecting a more uniform distribution of flexural stresses in said transition region between said crank arm and said crank spindle. 
 
     
     
       2. The exhaust-gas turbocharger according to  claim 1 , wherein said flexural-stress relief pocket extends in said crank arm in a radial direction toward the crank spindle axis of rotation as far as into a region of an outer diameter of said crank spindle, so as to undercut said abutment shoulder, and has a rounded contour at a pocket base formed there. 
     
     
       3. The exhaust-gas turbocharger according to  claim 2 , wherein said rounded contour on said pocket base has a radius of between 0.2 mm and 1.5 mm. 
     
     
       4. The exhaust-gas turbocharger according to  claim 2 , wherein said crank arm has reinforcement ribs and said flexural-stress relief pocket extends along said inner side of said crank arm and is delimited on both sides by in each case one of said reinforcement ribs. 
     
     
       5. The exhaust-gas turbocharger according to  claim 1 , wherein said reinforcement ribs have a height on said inner side of said crank arm selected such that said reinforcement ribs extend in a direction of the crank spindle axis of rotation at most as far as into a region of said abutment shoulder.